Apparatus for salvaging scrap metal

ABSTRACT

Large metallic structures such as vessels, railroad cars or the like are salvaged by disintegrating the structures into small, readily handled pieces of scrap metal for shipment of the pieces to a steel mill or the like. A portable shear is provided which comprises a tubular female shear member having a first arcuate cutting edge and a cylindrical male shear element which defines a second, cooperating cutting edge and which reciprocates within the tubular member. With the cutting edges in their spaced-apart positions the shear is placed over an edge of the structure and power means is actuated to move the cutting edges against each other and to thereby sever a relatively small piece of scrap metal from the structure. Thereafter, the cutting edges are retracted, the shear is relocated to another, e.g. adjacent portion of the structure and another piece of scrap metal is severed. The cutting edges are angularly inclined with respect to each other so that each piece is sequentially severed from the structure to thereby reduce the force that must be exerted to effect the shearing operation. Means is further provided to limit the maximum size of the severed piece to less than an interior opening of the tubular member so that the severed piece is readily removed therefrom without the exertion of a mechanical removal force.

This is a division, of application Ser. No. 464,596, now U.S. Pat. No.3,908,493, filed Apr. 25, 1974.

BACKGROUND OF THE INVENTION

An ever sparser supply of metal ore, particularly iron ore makes itincreasingly important to salvage old and surplus metal structures. Whenthe structures are relatively small, such as metal shavings and thelike, there is little problem in salvaging and reusing them as scrapmetal. Even larger structures such as passenger automobiles are readilysalvaged by placing them in presses and compacting them into smallcompressed metal packages which are then forwarded to a steel mill forremelting and manufacture into steel ingots and the like.

However, when the structures become larger their salvage becomes moredifficult since it is normally impossible to ship them to and use themin a steel mill due to their bulk and weight. They must therefore be cutor severed into smaller, more readily handled pieces. The salvage oflarge ocean-going vessels and railroad cars, for example, requires thatthe structure be cut up in the field and shipped to the mill before theycan be melted.

In the past such a structure, say a vessel, was salvaged bysystematically dismantling it, i.e., by torch or flame cutting it intosmaller components. Conventional hoisting equipment such as a crane thenlifts the components, say a portion of the vessel's bridge or a sectionof its hull on land where the component is further cut down in size withtorch cutting equipment or, to the extent presses are available byshearing the components into relatively small pieces of scrap metal. Ininstances where the vessel is not too far from a factory which has anindustrial shear available, it is also common to transport thedismantled components to the factory and there shear them into smallscrap metal pieces.

The ever-increasing price of scrap metal now makes such methodseconomically more feasible even though they require much manpower andconsume large amounts of expensive cutting gas. Furthermore, thecommonly encountered heavy layer or layers of paint, rust, organic orinorganic substances such as scum, barnacles, etc. on vessels beingsalvaged can make torch cutting difficult if not impossible.Conventional torch cutting equipment cannot cut through heavy layers ofrust, scum or paint and the paint has a tendency to sputter andgenerates so much smoke that it may impair the cutting operation, speedand accuracy. Thus, the rust, paint, etc. is ordinarily first scraped orburned off along the cutting line before the actual torch cuttingcommences to eliminate the mentioned problems and hazards.

Moreover, after the relatively large component has been dismantled andtransferred on dock or land, it must further be cut down in size tobecome scrap metal that is accepted by steel mills. Additionally,smaller size scrap yields higher scrap metal prices; it is thereforedesirable to cut the component into the smallest possible pieces subjectonly to limitations caused by the unit cutting costs. Thus, by the timethe vessel has been cut down to acceptably small pieces of scrap metal,the unit cost of the scrap metal is relatively high and/or the salesprice for the scrap is relatively low. Profit margins are thereforesmall which discourages the wisest possible salvage of old, surplusvessels and other metal structures. This in turn adversely affects theraw material supply and, in time, will necessarily tend to increasemetal costs.

SUMMARY OF THE INVENTION

The present invention provides an inexpensive method for salvagingvessels and similarly large metallic structures in the field by cuttingthe vessel into small, readily handled and accepted pieces of scrapmetal. In its broadest aspects the invention replaces the heretoforecommon flame cutting for dismantling the structures into largecomponents and hence into small pieces of scrap metal with a method bywhich the vessel is directly sheared into small pieces of scrap. Thisscrap is then collected and transported to the steel mill.

The present invention greatly facilitates the collection of the scrapsince the small pieces that are severed from the vessel can be permittedto drop into and collect in the hold of the vessel. For this purpose itis desirable to cut a sufficient number of holes in the deck andsubfloors so that the scrap can be readily collected. Moreover, it mayfurther be desirable to remove interior partitions and non-structuralwalls to provide sufficient unobstructed space.

After the superstructure and deck have been salvaged and the upper hulledge is a few feet above the waterline the scrap collected in the hullcan be removed with suitable magnets and the like for transfer torailroad cars, barges or transport ships. Furthermore, the hull can betowed to deeper waters for the transfer of the scrap to a waiting bargeor vessel. Thereafter, the remaining hull can be salvaged in accordancewith the present invention. Due to its relatively low weight it can alsobe hoisted on land to complete its salvage.

The present invention also provides a portable, power actuated shearwhich, in its preferred form, is defined by a tubular female die member(hereinafter sometimes referred to as "tube") and a cylindrical male diemember (hereinafter sometimes referred to as "piston") that isreciprocably disposed within the tube. The tube includes an concavefirst cutting die insert which defines a first cutting edge and whichcooperates with a complementarily shaped convex second die insert with asecond cutting edge. The press includes means, such as a semicircularcutout in the tube into which a portion of the structure, say steelplate, may be inserted. This cutout limits the depth to which the platemay be inserted to less than the full diameter of the tube so that whenthe shear is actuated a piece of scrap metal is severed from the platewhich has an outline that is less than the interior diameter of thetube. Consequently, the severed piece does not adhere to the tube butfreely drops therefrom under gravity without the need for exerting amecanical force for the removal of the piece. This greatly facilitatesthe ease and speed with which the shear can be operated and furtherreduces its power requirement.

It should be understood that the precise outline configuration of thecutting edge and of the severed scrap metal piece may be other thansemicircular. For example, the die inserts may be shaped to have square,triangular, elliptical or other compound outline configurations.Furthermore, the shear may be constructed so that the steel plateextends to more or less than one-half the interior tube diameter tobetter adapt the shear to a given application. What is important,however, is that the outline of the severed piece of scrap metal issmaller than the interior diameter of the tube for the reason statedabove.

For purposes of this specification and the claims the sheared piece ofscrap metal will frequently be referred to as having a "convex" outline,edge or configuration. By this is meant that one or more of the edges ofthe piece may be convexly shaped, or two or more contiguous edgesconverge upon each other as do, for example, two adjacent sides of atriangle.

When the severed piece has such a shape the cooperating die sections bynecessity have a complementary shape. One of the die sections, i.e., theouter or female section, then supports the bulk of the metal plate fromwhich the piece is cut along a complementary concave line which in turnprevents the formation of a bending moment when the two die sectionscontact the plate between them. As a consequence, neither the plate northe shear will wedge, tilt or pivot with respect to each other as couldoccur if the cutting edge were a straight edge as on conventional shearsor presses.

The shear of the present invention is used by moving the die insertsapart aligning the space therebetween with an edge of the vessel, say anedge of a hull plate, thereafter dropping the shear over the edge untilthe plate edge engages the end of the cutout in the tube, and thereafterpower actuating the die inserts to sever a generally semicircular pieceof scrap metal. To reduce power requirements it is preferred to shapethe cutting edge of at least one of the die inserts helically so that atany given moment only a short section of the total cutting edge lengthshears. Consequently, the scrap metal piece is sequentially shearedalong its shear line at a power requirement which is a fraction of whatit would be if the two cutting edges were parallel and simultaneouslyengaged the full length of the shear line. A smaller, lighter and lessexpensive shear can thus be used for cutting even heavy steel plate.

To adapt the shear of the present invention for use in disintegratingall parts of the vessel the cutout is relatively long in its axialdirection, say 18 to 24 inches long. Thus, heavy beams as well asrelatively thin steel plate may be sheared into scrap metal pieces bycorrespondingly retracting the die members a distance which is onlyslightly greater than the thickness of the portion being severed.

In another embodiment of the invention the circumferential cutout in thetube member is deleted and replaced by a slot in the piston. In thisembodiment the concave die insert is mounted to the end of the tube andthe piston protrudes past that end a sufficient distance so that theslot in the piston can reciprocate from without to within the tube,thereby passing the concave die insert. The axial end of the slotfurthest removed from the corresponding end of the tube when the slot isdisposed without the tube includes the cooperating concave die insert.The slot further extends a limited distance, say about one-half thediameter, into the piston to limit the depth to which a plate or otherportion of the vessel may be inserted. The actual cutting again takesplace by power actuating the piston so that the scrap metal piece is cutout at the tube end. When the piston is returned the severed piece ofscrap metal freely drops out of the slot. Thereafter the press isrepositioned as above described for severing the next piece of scrapmetal. Although it is preferred to use the above discussed shearconstruction for salvaging such objects as vessels, in a given instanceit might also be possible to salvage objects, particularly large plateswith scissor-like shears. Such an agreement normally requires at leasttwo angularly inclined cuts for severing a piece of scrap metal.Accordingly, such an approach will normally be economically lessdesirable.

Since the present invention shears the vessel into scrap metal theheretofore common flame cutting problems encountered when cuttingheavily painted, galvanized or rusty steel plates, beams and the likeare eliminated. Furthermore, the heretofore common initial dismantlingof the vessel into components which are then hoisted on land for furthercutting into scrap metal is replaced with one simple shearing operationto reduce material handling to a minimum. As the small pieces of scrapmetal are sheared off the vessel they drop to the ground, or to thebottom of the interior of the vessel, and are intermittently picked upwith suitable hoisting equipment such as hoisting magnets for transferto a shipping vehicle such as a railroad car. Thus, the presentinvention renders the salvaging of a vessel, a railroad car or the likesubstantially more simple as compared with prior art methods.

In addition, the actual metal cutting speeds are greatly increased.Flame or torch cutting of steel beams or plate progresses relativelyslowly and is measured in a few inches per minute. For dismantling avessel flame cuts having an aggregate length of hundreds and thousandsof yards are necessary. In contrast thereto, the present inventionemploys a quick shearing operation in which a single cut having a lengthof up to several feet is made in a matter of seconds. Thus, the scrapmetal cutting speed achieved with the present invention is many timesgreater than the cutting speed that could be attained with prior artsalvaging methods. This is in addition to the aforementionedsimplifications and speedup in the handling of the scrap. Consequently,whereas the complete salvage of a vessel in accordance with prior artmethods may have required as much as five to eight months it may now besalvaged in accordance with the present invention in as short a time asone to two months. Furthermore, in accordance with the present inventionthe salvaging operations can be carried on by a small crew of four tosix men whereas in the past the torch cutting, dismantling, transfer andfinal cutting of the components of the vessel required crews of up totwenty to thirty men. It is, therefore, apparent that the presentinvention provides great advantages over the prior art and greatlyincreases the economy with which a vessel may be salvaged.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, side elevational view of a section of a portionof a vessel being salvaged in accordance with the present invention;

FIG. 2 is a side elevational view of a portable press constructed inaccordance with the present invention and employed in salvaging thevessel illustrated in FIG. 1;

FIG. 3 is an enlarged cross-sectional view of the operative parts of thepress illustrated in FIG. 2;

FIGS. 4-7 are schematic illustrations of a hydraulic actuating mechanismand control for operating the portable press illustrated in FIG. 3;

FIG. 8 is a front elevational view, in section, of a portable pressconstructed in accordance with another embodiment of the presentinvention; and

FIG. 9 is a side elevational view, in section, and is taken along line9--9 of FIG. 8.

Referring to FIGS. 1 and 2, a vessel 2 floating in a body of water 4includes a hull 6 constructed of heavy steel plate 8 which is to besalvaged by disintegrating the steel plate into relatively small scrapmetal pieces 10 one of which is illustrated in FIG. 1 as dropping froman upper hull edge 12 into the body of water. In accordance with thepresent invention the vessel is salvaged with a portable shear 14 thatis suspended from a hoist or crane 16. Generally speaking, the shearincludes an outer tubular member or tube 18 which has a hollow interior,preferably a cylindrical interior 20 which receives and reciprocablymovably guides a cylindrical member of piston 22. A peripheral cutout 24is disposed between ends 26, 28 of the tube and extends overapproximately 180°. An axial end of the cutout mounts a semicircular dieinsert 30 which defines a concave cutting edge (not shown in FIGS. 1 and2). A complementary convex die insert 32 is mounted to one end of piston22. A power actuator 34 is provided for reciprocating piston 22 alongthe interior of tube 18 so that the cutting edges defined by die inserts30, 32 move past each other. Consequently, a portion of an object, say asteel plate or beam 36 placed between the retracted inserts (as shown inFIG. 2) is severed when power actuator 34 is energized to move theinserts past each other. The severed piece of scrap metal is dischargedthrough the interior of the tube past tube end 26.

In use shear 14 is hoisted above hull edge 12, piston 22 is retractedand cutout 24 is aligned with the hull edge so that the edge issubstantially perpendicular to the axis of the shear. The piston isretracted a sufficient distance so that when the shear is lowered overthe hull edge plate 8 can enter the space between the retracted dieinserts 30 and 32 until the hull edge engages an axially oriented end 38of the cutout. Power actuator 34 is now energized to force piston 22 tothe left, as seen in FIG. 2, until the cutting edges of the die insertshave moved past each other. At that point a generally semi-circularscrap metal piece 10 has been severed from the hull. By slightly tiltingthe shear the severed scrap metal piece will gravitationally drop fromthe interior of tube 18 since the piece is much smaller than thecylindrical interior so that tight frictional engagements, wedgings andthe like of the piece do not occur.

The power actuator is now energized to retract piston 22 to the positionillustrated in FIG. 2 and the shear is moved to the left, as seen inFIG. 1, along hull edge 12 for severing the next scrap metal piece fromthe hull. As is illustrated in FIG. 1 this results in a scalloped hulledge 40. The process is repeated over and over along the length of thehull, each time severing another essentially arcuately shaped,relatively small piece of scrap metal. The scrap metal drops to thebottom of the vessel, or to the ground or on suitable scrap collectingsurfaces mounted around the hull (not shown) and is intermittentlypicked up therefrom. The shear can be employed to cut along straight aswell as convex or concave metal edges. To cut a solid floor, say thedeck of the vessel, an initial hole of a sufficient diameter is burnedor severed into the floor so that the shear can be axially extendedtherethrough. With the shear in a vertical position the deck is thensevered into small pieces of scrap metal as above described. It isfurther possible to use shear 14 for salvaging under water structures,such a submerged vessels. For such an application the shear is used asabove described except that all operations are carried on while it issubmerged. Since the shear requires neither oxygen nor gas to sever thepiece of scrap metal from the submerged vessel complications which sofar prevented an economically feasable underwater salvage by torchcutting the vessel are eliminated.

Referring now to FIG. 3, a presently preferred embodiment of a portableshear 14 constructed in accordance with the invention is illustrated.Tube 18 is heavy walled and has a preferably slightly eccentriccylindrical interior 20 so that tube wall 42 opposite cutout 24 is ofgreater thickness than tube wall 44 aligned with the cutout.Furthermore, a gusset plate 46 is secured, i.e., welded to the exteriorof tube 18 and extends in axial direction beyond the ends of cutout 24to provide the tube with sufficient strength and rigidity as is furtherreferred to below.

Piston 22 is a hollow piston having an inner chamber 48 and a head 50which mounts die insert 32. The end of the piston opposite head 50 isdefined by a cover plate 52 which includes a concentric bore that isslidable over an elongate length of pipe 54 coaxially mounted to outertube 18. An inner end 56 of the pipe includes a coaxial disc 58 whichengages inner chamber 48 and which further includes seal rings 60 todivide the chamber into a first power chamber 62 and a second returnchamber 64.

The exterior surface of piston 22 includes an axially oriented groove orkeyway 66 which slidably engages a longitudinally oriented key 68secured to the interior surface 20 of tube 18. The key-keywayarrangement allows axial reciprocating travel of the piston but preventsrotational piston movements.

Pipe 54 is fixedly secured to a flange plate 70 that is bolted to and 28of tube 18. Pipe 54 comprises a double pipe having a first, centralpassage 72 which terminates in the first power chamber 62 and a second,annular passage 74 which terminates in a circular depression 76 of disc58 and which in turn communicates with return chamber 64.

It will now be apparent that piston 22 is axially movable along astraight line between a first, retracted position in which disc 58 isdisposed closely adjacent piston head 50 and in which convex die insert32 is relatively remote from concave die section 38 and a second pistonposition, in which disc 58 is closely adjacent to cover plate 52 and theconvex insert 32 has moved past the concave dye insert 30. During suchmovements pipe 54 and disc 58 as well as flange plate 70 remainstationary.

Referring now to FIGS. 3-7, the power driven operation of shear 14 inconnection with a presently preferred hydraulic power actuator 34 willbe described. FIGS. 4-7 schematically illustrate the hydraulic poweractuator and associated hydraulic equipment, conduits and controls.principally, they comprise a hydraulic pump 78 which communicates with areservoir 80 for hydraulic fluid and which has a downstream pressureconduit 82 that leads to a three-way valve 84. From the valve threeconduits lead to first and second power chambers 62 and 86 and thereturn chamber 64. For simplifying the description and schematicillustration each chamber is separately illustrated in the schematicFIGS. 4-7. In the shear illustrated in FIG. 3, the first power chamberis between piston head 50 and disc 58, the second power chamber 86 isbetween cover plate 52 and flange plate 70, and the return chamber isbetween cover plate 52 and disc 58. The first power chamber 62communicates with three-way valve 84 via conduit 72; the second powerchamber 86 communicates with the three-way valve via a conduit 88; andthe return chamber commuicates with the three-way valve via annularconduit 74 which in turn communicates with a tubular conduit 90 througha suitable passage 92 in end plate 70.

The first and second power chambers 62, 86 are provided foralternatively subjecting the piston to a lesser or greater axial force,respectively. When relatively thin-walled plate is sheared, the firstpower chamber is employed to thereby reduce fluid consumption duringoperation. When relatively heavy-walled plate is sheared the secondpower chamber, with its substantially larger effective piston area,alone or together with the first power chamber is employed. To effectthe necessary hydraulic switching a pair of two-way valves 94 areinterposed in hydraulic conduits 72 and 88 for connection of suchconduits with a pressurized fluid conduit or with a fluid return conduitto the reservoir 80.

The actual hydraulics operation is as follows. Pump 78 is energized andassuming first that a power stroke of intermediate force is desired,second power chamber 86 is energized by fluidly communicating it via theassociated two-way valve 94 with pressure conduit 82. Three-way valve isswitched so that return chamber 64 communicates with reservoir 80 fordischarging excess fluid from the return chamber to the reservoir whiletwo-way valve 94 associated with first pressure chamber 62 is switchedso that unpressurized fluid can be drawn from the reservoir to the firstpressure chamber. This switching arrangement is graphically illustratedin FIG. 4.

After completion of the power stroke, three-way valve is switched sothat pressure conduit 82 from pump 78 communicates with return chamber64 while pressure chambers 62 and 86 communicate with reservoir 80.Thus, the pressurized fluid in the return chamber forces piston 22 toits retracted position, illustrated in FIG. 7, while excess fluid inpressure chambers 62 and 86 is returned to the reservoir.

Assuming now a desired power stroke for piston 22 in which a maximumforce is exerted, three-way valve 84 is switched as illustrated in FIG.6 while two-way valve 94 associated with first power chamber 62 isswitched so that the first power chamber, in addition to the secondpower chamber 86 communicates with pressure line 82 from pump 78. Asbefore, return chamber 64 discharges excess fluid to reservoir 80. Inthis operating mode a maximum force is exerted for cutting heavy plateor beams, for example, while the piston travels relatively slowly. Onthe return stroke, three-way valve 84 is again positioned as earlierdescribed so that pressurized fluid fed to return chamber 64 forcespiston 22 into its retracted position while excess fluid from powerchambers 62 and 86 is returned to reservoir 80.

FIG. 5 illustrates the valving position for pressurizing small cylinder62 only. In this operating mode a relatively small force (for cuttingthin plate, for example) is exerted while the piston travels rapidly forhigh speed operation of the shear.

Referring again to FIG. 3, to further reduce power requirements during ashearing operation, and to facilitate the shearing of relatively heavyplate, say of up to one to two inches in thickness with a relativelylightweight and small portable shear, at least one of the die inserts,say convex insert 32 has a helically shaped cutting edge 96 whichcooperates with a circularly arcuate cutting edge 98 on insert 30. As aconsequence, only a short length of the cutting edges 96 and 98 overlapat any given moment. During a power stroke of piston 22, therefore, aplate 100 is sequentially sheared as a function of the extent of theaxial piston travel from a point of first engagement of the cuttingedges, at one arcuate end of inserts 30, 32, to a point of lastengagement at the other arcuate end of the inserts. Thus, at any giventime only a small portion of the overall cross section along the shearline is actually being severed. The required shearing power is thereforesubstantially reduced.

Since all shearing action is performed by die inserts 30, 32, they areconstructed of high quality tool steel to reduce the overall materialcosts for the shear. Furthermore, they are removably secured to the tubeand the piston, respectively, with suitable bolts (not separately shown)so that they can be replaced and/or sharpened.

Referring now briefly to FIGS. 8 and 9, another embodiment of theinvention contemplates the construction of shear 102 from a continuoustube 104 and a piston 106 reciprocably mounted in the above-describedmanner within the interior of the tube. A concave die insert 108 ismounted to an end 110 of the tube. The piston includes a slit 114disposed adjacent an end 112 of the piston which extend over an arc ofapproximately 180° to about the center of the piston. An axial edge 116of the slit furthest removed from tube 104 is provided with a convex dieinsert 118. The slit is preferably angularly inclined with respect tothe piston axis so that the convex die insert again defines a helicalcutting edge 120 while the concave insert defines a semicircular cuttingedge 122.

Shear 102 operates as follows. A power actuator 124 moves the pistoninto its retracted position in which slit 114 is wholly disposed outsidetube 104. A steel plate 126 (shown in phantom lines in FIG. 9) is placedinto the slit until the edge of the plate bottoms out against end wall128 of the slit. The power actuator is now energized to move the pistonin the opposite direction until die inserts 108 and 118 have passed eachother and the slit is wholly disposed within tube 104. A semicircularportion of plate 126 is thereby severed from the remainder of the plate.Upon reversal of the piston movement and after slit 114 is againdisposed outside tube 104 the severed semicircular piece of pate 126drops from the slit. The shear is now repositioned along plate edge asearlier described for severing the next piece.

The actual dimensioning of the shear is of course determined by itsapplication and the configuration of the structure which is to besalvaged therewith. In one practical embodiment of the invention, inwhich the shear is used for salvaging an ocean-going vessel ofintermediate size, say of approximately 1,000 to 1500 tons, thecylindrical interior 20 of tube 18 has a diameter of approximately 17 to18 inches with cutout 24 extending over 180°. Thus, the scrap metalpieces obtained with this press have a maximum size of 17 to 18 inchesby 81/2 to 9 inches and a semicircular configuration. It is of courseclear that as the salvaging operation progresses and shearing operationstake place in the already scalloped portion of the hull the shape of thesevered pieces will become irregular. This, however, in no way distractsfrom the value of the scrap metal pieces. Furthermore, the angularinclination of helical cutting edge 96 of insert 32 is between about 3°to about 10° . With such a configuration, the above-stated tubediameters and a fluid pressure of up to 5,000 psi plate as thick asseveral inches can be cut. Adjustments in the dimensioning of thecomponents of the shear to better adapt it for particular applicationscan of course be made.

Furthermore, to enable the use of the shear for severing plate as wellas relatively wide beams (see FIG. 2) cutout 24 preferably has an axiallength of at least about 12 to 18 inches so that even the thickest beamsencountered in vessels of the stated size can be placed in the cutoutand sheared off.

I claim:
 1. Apparatus for the infield salvage of large metal structuressuch as vessels or railroad cars and for disintegrating such structuresinto relatively small pieces of scrap metal, the apparatus comprising:atubular outer housing including first means defining a first, concavecutting edge; a plunger having a tubular portion, the plunger beingmovably disposed within the housing for movement along an interior ofthe housing, the plunger including second means defining a second,convex cutting edge cooperating with the first means for shearing scrapmetal pieces having an arcuate outline when a portion of the structureis disposed between the first and second means; whereby the first meansforms a stable support for the structure to prevent wedging of thestructure, the piece or the cutting edges when the cutting edges areforceably moved towards each other; a disc coaxially disposed within thehousing and within the tubular portion of the plunger and meansstationarily mounting the disc to the housing; means sealing the tubularplunger portion from the housing interior to thereby form sealed firstand second hollow chambers on respective sides of the disc; means foralternatively subjecting the chambers to a pressurized fluid to therebyreciprocate the plunger relative to the housing and the disc in an axialdirection so that the first means and the second means are moved towardsand past each other for severing a portion of the structure disposedbetween the first and second means into small pieces of scrap metal. 2.Apparatus according to claim 1 wherein the means for mounting the discto the housing comprises a pair of rigid, coaxial tubular membersdefining first and second coaxial fluid passages and extending through afirst end of the plunger, and including openings in the membersrespectively communicating the fluid passages with the first and secondchambers.
 3. Apparatus according to claim 2 wherein the second means isdisposed adjacent a second end of the plunger, and including meansestablishing a fluid-tight seal adjacent the first plunger end betweenan exterior of the plunger and the interior of the housing, and meansfor sealing an adjacent end of the housing to thereby define a third,fluid-tight chamber between the first plunger end and the adjacenthousing end, and including means for applying pressurized fluid to thethird chamber to thereby generate a force in addition to the forcegenerated when pressurized fluid is applied to the first chamber tothereby increase the cutting force exerted on the structure disposedbetween the concave and convex cutting edges.
 4. Apparatus for theinfield salvage of large metal structures such as vessels or railroadcars and for disintegrating such structures into relatively small piecesof scrap metal, the apparatus comprising:a tubular outer housingincluding a concave cutting edge and means for sealing one end of thehousing; a plunger having a tubular portion, the plunger being movablydisposed within the housing for movement along an interior of thehousing, the plunger including a convex cutting edge cooperating withthe convex edge for shearing scrap metal pieces having an arcuateoutline when a portion of the structure is disposed between the firstand second means, the plunger including means establishing a fluid tightseal between and exterior of the plunger and an interior of the housingto thereby define a fluid-tight first chamber between the plunger andsaid one end of the housing; a disc coaxially disposed within thehousing and within the tubular portion of the plunger and meansstationarily mounting the disc to the one end of the housing; meanssealing the tubular plunger portion from the housing interior to therebyform sealed second and third hollow chambers on respective sides of thedisc; means for alternatively subjecting the second and third chambersto a pressurized fluid to thereby reciprocate the plunger relative tothe housing and the disc in an axial direction so that the concave andthe convex cutting edges are moved towards and past each other forsevering a portion of the structure disposed between the edges intosmall pieces of scrap metal; and means for applying pressurized fluid tothe first chamber to thereby generate a force in addition to the forcegenerated when pressurized fluid is applied to one of the first andsecond chambers to thereby increase the cutting force exerted on thestructure disposed between the concave and convex cutting edges.